Hitt - The jump from 36mg to 24 was the biggest. We were both up to two packs a day, and 36 was the strongest juice we could find, at the time. In retrospect, it might have been a little too high, but it might also have been why we were able to stop smoking as soon as we started vaping. 36 was ....-kicking. 24 seemed comfortable. From there, we dropped to 18, then 12, with a little cross-over at each stop. For instance, right now, we're using almost as much 9mg as 12. Once we use up the 12, or find a way to cut it without loosing too much taste and satisfaction, I'll be introducing the 6 mg. I have a good stock of VG and PG, some nicotine, and some ideas. And the HV flavors are a great basis for these experiments. It hasn't been as uncomfortable as I thought it would be. In fact, sometimes the hardest part has been figuring out how much of what will give me the strength we need.
Don't have any mods, but we use 510 passthroughs at our desks. They're supposed to run at 5V, and they definitely kick up both the hit and the flavor.
Sorry for being so long-winded - you can tell, I'm committed to making this work for us. And I'm a loud-mouthed evangelist for PVs. Every smoker should at least try them.